The present invention relates to a stencil printing machine having a sheet transfer apparatus for discharging sheet formed with an image.
FIG. 21 shows a general stencil printing machine.
On one side of the stencil printing machine, there is provided a sheet supply base 100 loaded with print sheet P. The print sheet P is supplied to inside of the stencil printing machine by separating only a topmost sheet thereof by a separating roller 101.
The supplied print sheet P is transferred to a side of a printing drum 103 provided at inside of the stencil printing machine at predetermined timings by register rollers 102.
The printing drum 103 is constituted by forming an ink-permeable peripheral wall 104 in a cylindrical shape and is rotated in the counterclockwise direction of FIG. 21 around an axis line of the printing drum 103 per se. A perforated stencil sheet is wound around an outer peripheral face of the printing drum 103. At an inner portion of the printing drum 103, there is provided ink supply means 105 for supplying ink to an inner peripheral face of the printing drum 103. At outside of the printing drum 103, there is provided a press roller 106 moved attachably to and detachably from the outer peripheral face of the printing drum 103 at a position opposed to the ink supplying means 105.
Further, the print sheet P transferred by the register rollers 102, is brought into press contact with the stencil sheet disposed on the outer peripheral face of the printing drum 103 by the press roller 106 and one face thereof is transcribed with ink extruded from the inner peripheral face of the printing drum 103 via perforated portions of the stencil sheet.
The printed print sheet P is transferred by rotation of the printing drum 103 and is discharged to a sheet discharge base 109 provided on other side (side opposed to the sheet supply base 100) of the stencil printing machine by a sheet transfer apparatus according to a vacuum conveyor (suction belt) system having a vacuum fan 107 and a sheet transfer belt 108. A series of printing operation is carried out in this way.
In the above-described series of printing operation, the print sheet P brought into press contact to the side of the printing drum 103 by the press roller 106, is pasted to the side of the stencil sheet disposed on the outer peripheral face of the printing drum 103 by adhering force of ink.
Hence, conventionally, there is provided a separating claw 110 having a sharpened front end in front of the sheet transfer apparatus disposed on a sheet transferring side of the printing drum 103. The separating claw 110 catches the print sheet P pasted to the side of the printing drum 103 to thereby separate the print sheet P from the side of the printing drum 103.
Further, conventionally, in addition to (or in place of) the separating claw 110, there is provided an air blow fan 111 in front of the sheet transfer apparatus disposed on the sheet transferring side of the printing drum 103. By air blowing force of the air blow fan 111, the print sheet P is separated from the side of the printing drum 103.
However, according to the above-described conventional stencil printing machine, in the case of the separating claw 110, when the print sheet P is separated from the side of the printing drum 103, the separating claw 110 is brought into direct contact with the printed image face of the print sheet P and therefore, there poses a problem that an image portion is scraped and print quality is deteriorated.
Further, in the case of the air blow fan 111, there is produced a negative pressure region on the downstream side of an air flow at a vicinity of a blow out port thereof. Further, when the print sheet P is separated from the side of the printing drum 103, the print sheet P to be directed to the side of the sheet transfer apparatus, may be attracted to the side of the air blow fan 111 by suction operation of the negative pressure region and brought into contact with the blow out port of the air blow fan 111. Thereby, the image portion of the print sheet P is scraped similar to the case of the separating claw 110 and there poses a problem that the print quality is deteriorated.
Meanwhile, when a printing rate of the print image is large, that is, when a solid portion is large, the adhering force of ink is increased and the print sheet P becomes difficult to separate from the side of the printing drum 103. That is, time of separating the print sheet P from the side of the printing drum 103 is retarded and a time period of holding the print sheet P on the side of the printing drum 103 is prolonged.
Thereby, for example, although a transfer front end side of the print sheet P is going to be separated and transferred by the sheet transfer apparatus, a transfer rear end side thereof remains at the side of the printing drum 103 air without being separated from the side of the printing drum 103. Therefore, there poses a problem that the transfer rear end side of the print sheet P is flown up and in the worst case, sheet discharge jam is caused and the printing operation is interrupted.
Further, when the printing rate differs on the left and right sides of a direction of transferring the print sheet P, time of separating the print sheet P from the side of the printing drum 103 differs on the left side and on the right side. Thereby, there is a concern that transmission of the print sheet P to discharge is meandered or the sheet discharge jam is caused by the meandering.
Further, ink forms a printed image mainly by a mode of permeating to the print sheet P. However, when the time period of holding the print sheet P on the side of the printing drum 103, is long as mentioned above, ink of an amount more than necessary is transcribed to the print sheet P by the capillary phenomenon of ink.
When an amount of transcribing ink is as much as more than necessary in this way, the printed image portion is blotted to thereby deteriorate print quality or gradation is produced at a solid portion. Further, there causes a drawback that excess ink remaining on the surface of the print sheet P without being permeated, is brought into contact with a rear face of the print sheet P to be discharged successively and setoff is caused.
Although in each stencil sheet, the printing rate of the printed image respectively differs variously, when the printing rate differs considerably, a timing of separating the print sheet P from the side of the printing drum 103 differs.
That is, when the transfer front end side of the print sheet P is separated to the side of the sheet transfer apparatus, a track of exfoliating the transfer front end is changed and a position of the front end of the sheet is changed. Further, when the printing rate differs on the left side and on the right side of the transfer direction of the print sheet P, the print sheet P meanders as mentioned above and therefore, when the transfer front end side of the print sheet P is separated to the side of the sheet transfer apparatus, the position of the front end of the sheet meanders.
When the position of the front end of the print sheet P is changed in this way, particularly in the case of a stencil printing machine for carrying out multiple block printing or double-faced printing by providing other printing drum (not illustrated) at a post stage of the printing drum 103, there poses a problem that a printed image printed by the post stage of the printing drum shifts relative to the image of the print sheet P printed by the printing drum 103 at the initial stage.
Hence, in order to resolve the above-described problem, it is an object of the invention to provide a stencil printing machine capable of separating print sheet from a side of a printing drum and capable of separating print sheet from the side of the printing drum to align a position of a front end of sheet, regardless of a printing rate of printing and without being brought into contact with a printed image face of print sheet.
An explanation will be given of a constitution of the invention in order to achieve the above-described object in reference to the drawings in correspondence with embodiments.
That is, according to a first aspect of the invention, there is provided a stencil printing machine comprising:
a printing drum having an ink-permeable peripheral wall in a cylindrical shape and made rotatable around an axis line of the printing drum per se;
a squeegee roller for supplying ink from an inner peripheral face of the peripheral wall;
a press roller provided at outside of the printing drum for bringing a print sheet into press contact with a stencil sheet wound around an outer peripheral face of the peripheral wall between the squeegee roller and the press roller; and
exfoliation suction means for sucking the print sheet so as to exfoliate the print sheet from the printing drum;
the exfoliation suction means comprising:
a case having a guide plate at an upper face thereof and an exfoliation suction port at one end portion of the guide plate, the exfoliation suction port being arranged to be proximate to the press roller on a lower side of a reference line, the reference line being orthogonal to a center line of the squeegee roller intersecting with the axis line of the printing drum and passing through a position of bringing the press roller and the side of the printing drum into press contact with each other; and
a suction force generating portion for generating suction force to suck the print sheet toward the exfoliation suction port so as to exfoliate the print sheet from the printing drum, the suction force generating portion being provided at the case.
According to a second aspect of the invention, there is provided the stencil printing machine according to the first aspect wherein the suction force generating portion is provided to be proximate to a side of the exfoliation suction port.
According to a third aspect of the invention, there is provided the stencil printing machine according to the first aspect wherein the exfoliation suction port is provided at an upper end edge of the case constituting the one end portion side of the guide plate, and the exfoliation suction means further comprises a transfer section for transferring the print sheet, the transfer section having:
one pulley disposed at a vicinity of the exfoliation suction port in the case and axially supported by one end portion side of the guide plate;
the other pulley axially supported by other end portion side of the guide plate;
a support shaft provided at an opening portion of the exfoliation suction port; and
a transfer belt formed in an endless shape and hung around the pulleys and the support shaft so as to enter from the exfoliation suction port into the case;
the transfer section for driving an upper side portion of the transfer belt along an upper face of the guide plate.
According to a fourth aspect of the invention, there is provided the stencil printing machine according to the first aspect wherein the exfoliation suction means further comprises:
a transfer section for hanging a transfer belt formed in an endless shape around a pair of pulleys axially supported by one end portion side and other end portion side of the guide plate so as to drive an upper side portion of the transfer belt along an upper face of the guide plate; and
a guide rib for supporting the print sheet exfoliated from the side of the printing drum at the exfoliation suction port without bending the print sheet so as to guide the print sheet toward the transfer belt.
According to a fifth aspect of the invention, there is provided the stencil printing machine according to the first aspect wherein a plurality of the printing drums are provided via the exfoliation suction means.
According to a sixth aspect of the invention, there is provided a stencil printing machine comprising:
a printing drum having an ink-permeable peripheral wall in a cylindrical shape and made rotatable around an axis line of the printing drum per se;
a squeegee roller for supplying ink from an inner peripheral face of the peripheral wall;
a press roller provided at outside of the printing drum for bringing a print sheet into press contact with a stencil sheet wound around an outer peripheral face of the peripheral wall between the squeegee roller and the press roller;
suction transfer means for sucking the print sheet so as to exfoliate the print sheet from the printing drum to thereby transfer the print sheet, the suction transfer means comprising: a case having a guide plate at an upper face thereof and an exfoliation suction port provided at one end portion of the guide plate, the exfoliation suction port being arranged to be proximate to the press roller on a lower side of a reference line, the reference line being orthogonal to a center line of the squeegee roller intersecting with the axis line of the printing drum and passing through a position of bringing the press roller and a side of the printing drum into press contact with each other; a suction force generating portion for generating suction force, the suction force generating portion being provided at the case; and a transfer section for transferring the print sheet, the transfer section having: one pulley disposed at a vicinity of the exfoliation suction port and axially supported by one end portion side of the guide plate; the other pulley axially supported by other end portion side of the guide plate; and an endless shaped transfer belt with a vent hole formed therein hung around the pulleys so as to enter from the exfoliation suction port into the case, the transfer section driving an upper side portion of the transfer belt along an upper face of the guide plate;
wherein the guide plate has a transfer suction port overlapping the vent hole of the transfer belt, and the suction force generating portion generates suction force for sucking the print sheet toward the exfoliation suction port so as to exfoliate the print sheet from the printing drum and for sucking the exfoliated print sheet toward the vent hole and the transfer suction port overlapped each other so as to adsorb the exfoliated print sheet onto the transfer belt.
According to a seventh aspect of the invention, there is provided the stencil printing machine according to the sixth aspect wherein the suction force generating portion is provided to be proximate to a side of the exfoliation suction port.
According to an eighth aspect of the invention, there is provided the stencil printing machine according to the sixth aspect wherein the exfoliation suction port is provided at an upper end edge of the case constituting the one end portion side of the guide plate, the one pulley is disposed in the case, the transfer section has a support shaft provided at an opening portion of the exfoliation suction port, and the transfer belt is hung around the pulleys and the support shaft so as to enter from the exfoliation suction port into the case.
According to a ninth aspect of the invention, there is provided the stencil printing machine according to the sixth aspect wherein said stencil printing machine is formed such that a total opening area of the transfer suction port is smaller than a total opening area of the exfoliation suction port.
According to a tenth aspect of the invention, there is provided the stencil printing machine according to the sixth aspect wherein the suction transfer means is provided with a guide rib for supporting the print sheet exfoliated from the side of the printing drum at the exfoliation suction port without bending the print sheet so as to guide the print sheet toward the transfer belt.
According to an eleventh aspect of the invention, there is provided the stencil printing machine according to the sixth aspect wherein a plurality of the printing drums are provided via the suction transfer means.